It's NOT true that nickel is non-toxic. It's in fact rather highly toxic as heavy metals go, and it doesn't take much in the body to cause severe problems. Many if not most nickel factory workers were poisoned in the old and not-so-old days.

In Germany, there was a recent scandal when it was discovered by testing that the cheaper kind of electric kettle ("Wasserkocher"), as found in every German kitchen, with the exposed nickel-plated steel heating element in contact with the water, was putting worrisome amounts of nickel into everyone's hot water. I threw ours out. (Better and newer ones have the heating element beneath a stainless-steel bottom plate.)

Zinc in small amounts is needed for health, and not nearly as toxic.

So, like all other batteries, these should never be taken apart and must be properly recycled, at a facility that can handle this new chemistry.